Intro for Design Guide for Slabs-on-Ground ACI 360R-10 .pdf

ACI 360R-10

Guide to Design of Slabs-on-Ground

Reported by ACI Committee 360

First Printing April 2010 ®

American Concrete Institute Advancing concrete knowledge

Guide to Design of Slabs-on-Ground

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www.concrete.org ISBN 978-0-87031-371-4

ACI 360R-10

Guide to Design of Slabs-on-Ground Reported by ACI Committee 360 Wayne W. Walker Chair

Robert B. Anderson Vice Chair Philip Brandt Secretary

J. Howard Allred Carl Bimel

Edward B. Finkel Barry E. Foreman

Donald M. McPhee Steven N. Metzger

Nigel K. Parkes Roy H. Reiterman

Joseph A. Bohinsky William J. Brickey

Terry J. Fricks Patrick J. Harrison

John P. Munday Joseph F. Neuber, Jr.

John W. Rohrer Scott M. Tarr

Joseph P. Buongiorno Allen Face

Paul B. Lafontaine Ed T. McGuire

Russell E. Neudeck Scott L. Niemitalo

R. Gregory Taylor Donald G. W. Ytterberg

C. Rick Felder

Andrew W. McKinney

This guide presents information on the design of slabs-on-ground, primarily industrial floors. It addresses the planning, design, and detailing of slabs. Background information on design theories is followed by discussion of the types of slabs, soil-support systems, loadings, and jointing. Design methods are given for unreinforced concrete, reinforced concrete, shrinkage-compensating concrete, post-tensioned concrete, fiber-reinforced concrete slabs-on-ground, and slabs-on-ground in refrigerated buildings, followed by information on shrinkage and curling. Advantages and disadvantages of these slab design methods are provided, including the ability of some slab designs to minimize cracking and curling more than others. Even with the best slab designs and proper construction, it is unrealistic to expect crack-free and curl-free floors. Every owner should be advised by the designer and contractor that it is normal to expect some cracking and curling on every project. This does not necessarily reflect adversely on the adequacy of the floor’s design or quality of construction. Design examples are given. Keywords: curling; design; floors-on-ground; grade floors; industrial floors; joints; load types; post-tensioned concrete; reinforcement (steel, fibers); shrinkage; shrinkage-compensating; slabs; slabs-on-ground; soil mechanics; warping.

ACI Committee Reports, Guides, Manuals, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom. Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer.

CONTENTS Chapter 1—Introduction, p. 360R-3 1.1—Purpose and scope 1.2—Work of ACI Committee 360 and other relevant committees 1.3—Work of non-ACI organizations 1.4—Design theories for slabs-on-ground 1.5—Construction document information 1.6—Further research Chapter 2—Definitions, p. 360R-5 2.1—Definitions Chapter 3—Slab types, p. 360R-6 3.1—Introduction 3.2—Slab types 3.3—General comparison of slab types 3.4—Design and construction variables 3.5—Conclusion Chapter 4—Soil support systems for slabs-on-ground, p. 360R-8 4.1—Introduction 4.2—Geotechnical engineering reports 4.3—Subgrade classification 4.4—Modulus of subgrade reaction 4.5—Design of slab-support system 4.6—Site preparation ACI 360R-10 supersedes ACI 360R-06 and was adopted and published April 2010. Copyright © 2010, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.

360R-1

360R-2

ACI COMMITTEE REPORT

4.7—Inspection and site testing of slab support 4.8—Special slab-on-ground support problems Chapter 5—Loads, p. 360R-18 5.1—Introduction 5.2—Vehicular loads 5.3—Concentrated loads 5.4—Distributed loads 5.5—Line and strip loads 5.6—Unusual loads 5.7—Construction loads 5.8—Environmental factors 5.9—Factors of safety Chapter 6—Joints, p. 360R-22 6.1—Introduction 6.2—Load-transfer mechanisms 6.3—Sawcut contraction joints 6.4—Joint protection 6.5—Joint filling and sealing Chapter 7—Design of unreinforced concrete slabs, p. 360R-31 7.1—Introduction 7.2—Thickness design methods 7.3—Shear transfer at joints 7.4—Maximum joint spacing Chapter 8—Design of slabs reinforced for crack-width control, p. 360R-34 8.1—Introduction 8.2—Thickness design methods 8.3—Reinforcement for crack-width control only Chapter 9—Design of shrinkage-compensating concrete slabs, p. 360R-34 9.1—Introduction 9.2—Thickness determination 9.3—Reinforcement 9.4—Other considerations Chapter 10—Design of post-tensioned slabs-on-ground, p. 360R-38 10.1—Introduction 10.2—Applicable design procedures 10.3—Slabs post-tensioned for crack control 10.4—Industrial slabs with post-tensioned reinforcement for structural support Chapter 11—Fiber-reinforced concrete slabs-on-ground, p. 360R-40 11.1—Introduction 11.2—Synthetic fiber reinforcement 11.3—Steel fiber reinforcement Chapter 12—Structural slabs-on-ground supporting building code loads, p. 360R-44 12.1—Introduction 12.2—Design considerations

Chapter 13—Design of slabs for refrigerated facilities, p. 360R-44 13.1—Introduction 13.2—Design and specification considerations 13.3—Temperature drawdown Chapter 14—Reducing effects of slab shrinkage and curling, p. 360R-45 14.1—Introduction 14.2—Drying and thermal shrinkage 14.3—Curling and warping 14.4—Factors that affect shrinkage and curling 14.5—Compressive strength and shrinkage 14.6—Compressive strength and abrasion resistance 14.7—Removing restraints to shrinkage 14.8—Base and vapor retarders/barriers 14.9—Distributed reinforcement to reduce curling and number of joints 14.10—Thickened edges to reduce curling 14.11—Relation between curing and curling 14.12—Warping stresses in relation to joint spacing 14.13—Warping stresses and deformation 14.14—Effect of eliminating sawcut contraction joints with post-tensioning or shrinkage-compensating concrete 14.15—Summary and conclusions Chapter 15—References, p. 360R-53 15.1—Referenced standards and reports 15.2—Cited references Appendix 1—Design examples using Portland Cement Association method, p. 360R-58 A1.1—Introduction A1.2—The PCA thickness design for single-axle load A1.3—The PCA thickness design for slab with post loading A1.4—Other PCA design information Appendix 2—Slab thickness design by Wire Reinforcement Institute method, p. 360R-60 A2.1—Introduction A2.2—The WRI thickness selection for single-axle wheel load A2.3—The WRI thickness selection for aisle moment due to uniform loading Appendix 3—Design examples using Corps of Engineers’ charts, p. 360R-63 A3.1—Introduction A3.2—Vehicle wheel loading A3.3—Heavy lift truck loading Appendix 4—Slab design using post-tensioning, p. 360R-63 A4.1—Design example: Post-tensioning to minimize cracking A4.2—Design example: Equivalent tensile stress design Appendix 5—Design example using shrinkagecompensating concrete, p. 360R-65 A5.1—Introduction

DESIGN OF SLABS-ON-GROUND

A5.2—Example selecting the optimum amount of reinforcement to maximize the compressive stress in the concrete where the slab thickness, the joint spacing, and prism expansion are known Appendix 6—Design examples for steel FRC slabson-ground using yield line method, p. 360R-66 A6.1—Introduction A6.2—Assumptions and design criteria Appendix 7—Construction document information, p. 360R-67 A7.1—Introduction A7.2—Example design criteria A7.3—Typical details Conversion factors, p. 360R-72 CHAPTER 1—INTRODUCTION 1.1—Purpose and scope This guide presents information on the design of slabs-onground. Design is the decision-making process of planning, sizing, detailing, and developing specifications preceding construction of slabs-on-ground. Information on other aspects, such as materials, construction methods, placement of concrete, and finishing techniques is included only where needed in making design decisions. In the context of this guide, slab-on-ground is defined as: a slab, supported by ground, whose main purpose is to support the applied loads by bearing on the ground. The slab is of uniform or variable thickness and it may include stiffening elements such as ribs or beams. The slab may be unreinforced or reinforced with nonprestressed reinforcement, fibers, or posttensioned tendons. The reinforcement may be provided to limit crack widths resulting from shrinkage and temperature restraint and the applied loads. Post-tensioning tendons may be provided to minimize cracking due to shrinkage and temperature restraint, resist the applied loads, and accommodate movements due to expansive soil volume changes. This guide covers the design of slabs-on-ground for loads from material stored directly on the slab, storage rack loads, and static and dynamic loads associated with equipment and vehicles. Other loads, such as roof loads transferred through dual-purpose rack systems, are also mentioned. This guide discusses soil-support systems, shrinkage and temperature effects; cracking, curling or warping; and other concerns affecting slab design. Although the same general principles are applicable, this guide does not specifically address the design of roadway pavements, airport pavements, parking lots, or mat foundations. 1.2—Work of ACI Committee 360 and other relevant committees There are several ACI committees listed below that provide relevant information concerning slabs-on-ground design and construction or similar slab types that are not addressed in this guide such as pavements, parking lots, or mat foundations. These committees provide documents where more detailed information for topics discussed in this guide can be found.

360R-3

1.2.1 ACI Committee 117 develops and reports information on tolerances for concrete construction through liaison with other ACI committees. 1.2.2 ACI Committee 223 develops recommendations on the use of shrinkage-compensating concrete. 1.2.3 ACI Committee 301 develops and maintains specifications for concrete construction. 1.2.4 ACI Committee 302 develops and reports information on materials and procedures for the construction of concrete floors. ACI 302.1R provides guidelines and recommendations on materials and slab construction. ACI 302.2R provides guidelines for concrete slabs that receive moisture-sensitive flooring materials. 1.2.5 ACI Committee 318 develops and maintains building code requirements for structural concrete. 1.2.6 ACI Committee 325 develops and reports information on concrete pavements. 1.2.7 ACI Committee 330 develops and reports information on concrete parking lots and paving sites. Parking lots and paving sites have unique considerations that are covered in ACI 330R. 1.2.8 ACI Committee 332 develops and reports information on concrete in residential construction. 1.2.9 ACI Committee 336 develops and reports information on footings, mats, and drilled piers. The design procedures for combined footings and mat foundations are given in ACI 336.2R. Mat foundations are typically more rigid and more heavily reinforced than common slabs-on-ground. 1.2.10 ACI Committee 360 develops and reports information on the design of slabs-on-ground, with the exception of highways, parking lots, airport pavements, and mat foundations. 1.2.11 ACI Committee 544 develops and reports information on concrete reinforced with short, discontinuous, randomlydispersed fibers. ACI 544.3R is a guide for specifying, proportioning, and production of fiber-reinforced concrete (FRC). 1.3—Work of non-ACI organizations Numerous contributions of slabs-on-ground design and construction information used in this guide come from organizations and individuals outside the American Concrete Institute. The U.S. Army Corps of Engineers (USACE), the National Academy of Science, and the Department of Housing and Urban Development (HUD) have developed guidelines for floor slab design and construction. The Portland Cement Association (PCA), Wire Reinforcement Institute (WRI), Concrete Reinforcing Steel Institute (CRSI), Post-Tensioning Institute (PTI), as well as several universities and consulting engineers have studied slabs-on-ground and developed recommendations for their design and construction. In addition, periodicals such as Concrete International and Concrete Construction have continuously disseminated information about slabs-on-ground. 1.4—Design theories for slabs-on-ground 1.4.1 Introduction—Stresses in slabs-on-ground result from applied loads and volume changes of the soil and concrete. The magnitude of these stresses depends on factors such as the degree of slab continuity, subgrade strength and